Very thin, delicate tissue samples (known as tissue sections) are commonly to collected and prepared for analysis such as molecular testing or microscopy. Tissue sections are often obtained by slicing from a formalin fixed, paraffin embedded (FFPE) blocks of a tissue via a variety of methods. Some known methods include: (1) cutting sections of a tissue block using a microtome; (2) scraping a tissue sample off of a slide by using a razor blade; (3) identifying a portion of a tissue sample and macrodissecting this portion using a variety of suitable tools; or (4) performing laser-capture microdissection (LCM). For example, microtomes are used to cut extremely thin slices of tissue for microscopic observation under transmitted light or electron radiation. Microtomes use extremely sharp knives to slice thin tissue sections of a desired thickness from a sample. A thin tissue section may curl or forming a roll of tissue section. Steps may be taken to prevent the tissue section from forming a roll on a surface after being sliced. Such steps may be taken so that the tissue section can be placed on a microscope slide for observation.
Tissue sections can be retrieved from a slicing surface such as the knife plate of a microtome. The retrieval of the tissue section is usually done manually, such as by an operator using a grasping tool. The operator then may transfer to a slide or to a vessel for further processing. Because the tissue sections are extremely thin, with some having a few micron thickness, they may be difficult to collect and transfer without damage or contamination.
In many laboratories and tissue sectioning systems, the transferring process is a manual process. This can slow down the work flow process when preparing tissue sections for molecular testing. Another problem associated with manual processes is that the tissue samples can be contaminated during the transfer. Nonetheless, transfer of thin tissue sections is necessary for additional processing of the tissue, particularly if molecular testing is desired. It is often desirable to transfer a tissue section to a suitable container, such as a microcentrifuge tube, for processing such as removal of paraffin.
Laser-capture microdissection is described in more detail in Gross et al., “Technologies for Single-Cell Isolation”, Int. J. Mol. Sci. 2015, 16(8), 16897-16919. A tissue section is observed through a microscope and the target cell or compartment is visually identified. The laser cuts the tissue and the isolated cell (or compartment) can be extracted. Contact-based extraction can be done via adhesion, employing adhesive tube caps or heat-absorbing transfer foils, locally made adhesive by infrared (IR) lasers. Contact-free gravity-assisted microdissection (GAM) uses an inversely mounted substrate placed over a collector tube. Once being cut out by the laser, the target cell (or compartment) falls down into the collector.
There remains a need for better tools and processes to improve the transferring tissue samples, particularly tissue sections which are very thin and delicate, without damage or contamination.